Dental tool drive mechanism



March 22, 1966 c. A'. ELLIS DENTAL TOOL DRIVE MECHANISM Filed March 20, 1959 INVENTOR. CHARLES A. ELLIS United States Patent 3,241,239 DENTAL TOOL DRIVE MECHANISM Charles A. Ellis, Point Road, Marion, Mass. Filed Mar. 20, 1959, Ser. No. 800,717 2 Claims. (Cl. 32-27) This invention relates to dental apparatus and more particularly to air powered dental tool driving devices or handpieces as they are called. The subject invention is further limited to that class of air driven handpieces which impart a reciprocatory motion to the cutting tool as opposed to those which drive the tools in a continuous rotary motion.

In one type of dental handpiece used in present day practice, the dental tool is rotated at extremely high speed by a miniature turbine driven by compressed air. These devices are ideal for their intended purpose of removing tooth substance at a controlled high rate. They are, however, quite unsatisfactory for the work known as polishing which is performed upon the exposed tooth surfaces, particularly after cleaning and removal of calculus deposits. The very high rotational speeds and high cutting capacity of such turbine driven devices makes them impractical to control on the exposed surfaces.

Conventional practice is to revert to the low speed, electromechanically driven rotating handpieces. These are capable of satisfactory control but are inherently handicapped in that the rotary motion imparted to the tool does not permit following of the tooth surfaces as intimately as is desirable, and the proximity of the gums forces the dentist to polish across the tooth near the gum line rather than longitudinally of the tooth in the direction of its natural imperfections of surface.

Another shortcoming of present tools is the centrifugal flinging of abrasive material from the working area.

As a result of the divergent needs of the dentist and the limitations of currently available tools, two types of tool driving equipment have become necessary. This is highly undesirable in that it is costly in the first place and more important the dual power supply is costly to maintain.

Accordingly, a primary object of this invention is to provide a new and novel construction for the driving mechanism of an air powered dental handpiece and tools for polishing teeth.

Another object of this invention is to provide a reciprocating motion to said tools for effectively following the natural imperfections of tooth surfaces.

Another object of this invention is to provide in said tools surfaces corresponding to the tooth surfaces to be polished.

Another object of this invention is to provide, in a reciprocating tool for polishing teeth, a mechanism with a minimum number of wearing parts.

Still another object of the invention is to minimize the loss of abrasive substance by which the polishing is accomplished.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings and it will be apparent that many changes may be made in the details of construction and arrangement of parts shown and described without departing from the spirit of the invention as expressed in the accompanying claims. I, therefore, do not wish to be limited to the exact details of the construction and arrangement of parts shown and described as the preferred form only is given by way of illustration.

Referring to the drawings:

, FIG. 1 is a side elevational view of a reciprocatory dental handpiece which incorporates the invention;

3 ,241,239 Patented Mar. 22, 1966 FIG. 2 is an enlarged side sectional view of the head end of the handpiece of FIG. 1;

FIG. 3 is an enlarged side sectional view of the distal end of the handpiece of FIG. 1;

FIG. 4 is an enlarged front elevational view of the polishing tool of FIG. 1;

FIG. 5 is a side elevational view of the tool of FIG. 4;

FIG. 6 is an enlarged sectional view of the tool of FIG. 5 taken substantially along the line 66 of FIG. 5, in the direction of the arrows;

FIG. 7 is a sectional view of a modification of the tool of FIG. 6;

FIISIICE 8 is a sectional view of a second modification of FIG. 9 is a front elevational view of another variety of polishing tool.

Referring now to FIG. 1, there is shown a. dental handpiece which incorporates the invention. This handpiece is of the air-powered reciprocating type and comprises a tubular handle section, designated generally by the numeral 11, at the forward end of which is securely attached a head, designated generally by the numeral 12. As will be explained hereinafter, a polishing tool, designated generally by the numeral 13, may be securely po sitioned in the head 12. At the opposite end of the handle section is attached a flexible tubular air pressure line 14 which is in turn connected to a suitable source of regulated compressed air (not shown).

Details of the head are most clearly shown in FIG. 2. A cylinder 15 is securely attached, by brazing or other suitable means, to a mounting stub 16, in a suitable angular relationship. The cylinder has a longitudinal bore 17, said bore being enlarged at one section 18, and constricted concentrically at another section 19.. The cylinder is permanently capped at one end by cap member 29 and has a removable cap 21 at the other end thereof. Cap 21 is threadedly secured at 31 to cylinder 15 in conventional manner and is fitted with gasket 21' to prevent leakage of compressed air from the cylinder. Within the cylinder, and designed for reciprocating motion therein, is a piston, generally designated by the numeral 22. The piston 22 is generally cylindrical in form and has two diameters, one end 23 designed for sliding fit with bore 17, and the other end 24 reduced in diameter and designed for sliding fit within constriction 19. Stub support member 16 is of hollow tubular form and its bore 25 forms the air passage for compressed air from handle section 11 to the cylinder 15. Communicating with bore 25 is inlet port. 26 through the side of cylinder 15. Also through the cylinder wall are a multiplicity of exit ports 27 for the exhaust of the used compressed air. Piston 22 has a deep axial bore 28 extending from the large end nearly to but not through the opposite end. Communicating with bore 28 are two groups of ports, the head end inlet ports 29 and piston exhaust ports 30. The removable cap 21 is threaded at one end 31 for engagement with the cylinder 15 and carries at its opposite end a tapered bore 32 which acts as a tool holding socket for a tool such as 13 shown in FIG. 1. The stub support member 16 carries, adjacent the end away from the cylinder, a circumferential groove 33 in which sealing ring 34 is held. When handle section 11 is telescoped over member 16, ring 34 provides an effective seal against the escape of compressed air, and air passage 36 in handle 35 is effectively coupled to bore 25. The coupling is maintained by screw 37, the head of which engages a recessed seat in member 16 and passes through a tight fitting hole 38, in handle 35.

The means of attachment of air supply 14 to the handle section 11 is best shown in FIG. 3. Handle 35 is enlarged for a portion of its length near the attachment end and the air passage 36 is enlarged, as shown at 36, in this portion for the purpose of holding an air filter generally represented by numeral 56. A cap 39 is threadedly connected to the handle in the conventional manner. A circumferential groove 40 in cap 39 retains a sealing ring 41 for sealing against leakage of air when the parts are in telescoping relation. Extending through the cap on its axis is a bore for the passage of air supply 14. The outermost end of this cap is smoothly contoured at 39 and the bore is flared as shown at 42 to provide an effective strain relief for the flexible tube of the air supply 14. The inward end of the bore is likewise flared for a short distance as shown as 4-3, the flare leading into a cylindrical section 44 which is further reduced to another cylindrical section at 45. Section 45 is a snug fit upon the unexpanded tubing 14-. A cylindrical sleeve it; with a bore 47 and a smoothly contoured end 48 is pressed into the end of the tubing 14. The tubing 14, with expanding sleeve 46 in place, is then pressed into the bore 44, thus forming an anchoring means for attachment of tubing 14' to cap 3d. The flare 42 and cylindrical section 45 prevents bending from reaching the heavily stressed anchoring area of the tubing.

Referring now to FIGS. 4 and 5, a polishing tool consists of a working face 49, and a mounting shank Stl arranged at a suitable angle to the working surface as represented by numeral 51. The shank 5d has a tapered portion 52 adapted to wring fit into tool holding socket 32 of the head 12. The wrking, or tooth contacting surface, may take any of several forms. For polishing the labial or outside surfaces of teeth a generally concave surface as in FIG. 8 is most satisfactory since it conforms more nearly to the convex tooth surfaces. For the lingual surfaces which are of more complex form convex and flat working surfaces are necessary. It is also advantageous to have the tool edges properly shaped for the particular polishing area. A flat ended tool as in FIG. 4 permits close approach to the gum line and a tapered point as in FIG. 9 is very effective in reaching deep into the crevices between teeth. For the purpose of holding abrasive slurry, generally used as a polishing agent, the surface 49 may be indented in random pattern with a multiplicity of tiny depressions 53 as shown in FIGS. 4 and 6. In FIG. 7 is shown a construction wherein an abrasive surface 54 is adhered to the working surface and is thus not subject to throwing of the abrasive out of the polishing area. Similar means are provided in the tool of FIG. 8 wherein abrasive particles 55, are embedded directly in and adhered to the working surface. The tool material in all cases must be of a somewhat elastic material, softer than tooth enamel or the abrasive material. It should permit embedment of abrasive rather than be severely abraded by it. These requirements are best fulfilled by plastic materials of the thermo-plastic class. Among the softer types celluose acetate is satisfactory. A harder but still satisfactory type of material are the polyamide class resins. The bonding characteris tics of these plastic materials are most advantageous in preparing tools of the types of FIG. 7 and FIG. 8. The working surface of such a tool is wetted with a proper solvent such as acetone for a tool formed of cellulose acetate. As the solvent acts upon the plastic and evaporates, it leaves a tacky surface. To this surface may be applied a small section of abrasive impregnated fabric material as illustrated by numeral 54-, and the bond thus formed will be secure and water resistant. Alternatively, abrasive powder may be applied directly to the tacky surface as illustrated at 55, and it will be securely held in sufiicient quantity. A tool thus prepared has a harder cutting characteristic than that to which the impregnated fabric is applied though its cutting life is somewhat shorter than that of the impregnated fabric tool.

The selected tool is driven in a vibratory and reciprocatory manner by the reaction eflfects of the piston 22,

moving back and forth in the cylinder 15. It is to be noted that there is no relative motion of other parts, aside from their elasticity, piston 22 being the only moving part. It is centered in the cylinder 15 by a thin film of leakage air and it does not make metallic contact with the end caps, being arrested by the timing of the port system. Compressed air from the supply (not shown) passes through the flexible pressure line 14, thence through bore 47, filter St; in bore 36', bore 35, bore 25 to inlet port 26. With piston in position shown in PlG. 2, incoming compressed air passing through port 26 surrounds the small diameter 24 of the piston between constriction 19 of the cylinder, and the step 23' of the larger piston diameter 23. This produces a net leftward. thrust to the piston and motion to the left until the step 23 comes into alignment with the edge of bore enlargement 18. At this point air may escape around step 23, into the annular space of bore 18, thence through the head end ports 29 and into bore 17. As a result air pressure is exerted over the total area of the enlarged piston end 23, in a rightward direction. The area involved is greater than the area of step 23 so a net rightward force results, causing a reversal of piston motion. This motion first causes sealing off of head and ports 29 and then piston exhaust ports 30 to be uncovered at the right edge of constriction 19, thus allowing release of pressure from the head end. Air exhausted from ports 30 passes through bore 17 and thence through exit ports 27 to the atmosphere. As soon as the pressure in the head end has been sufliciently reduced the constant leftward thrust upon step 23' once more gains control and reverses the motion, sealing exhaust ports 39. When the step 23 reaches the edge of bore 13 it provides another head end event. The speed with which this cycle repeats is related to the pressure of the incoming compressed air, the mass of the piston and the relative size and timing of the various ports.

For the purpose at hand, it is desirable that the frequency of vibration be low enough to avoid physiological damage to the tooth or its supporting structures by causing standing waves therein. There is some evidence in the literature that ultrasonic vibrations may cause such damage. For this reason the design speed of the subject device should be restricted to not over 2500 cycles per second.

The rapid vibration of the piston 22, causes a vibratory reaction of the entire handpiece. The point of support in the hand becomes a generalized instantaneous center of rotation and as a result, the motion of the tool holding end 21, of head 12, generates a somewhat rectangular path in the plane of intersection of handle and head. The long sides of the rectangle are produced by the vigorous translatory reaction to the piston, the smaller lateral action is due to the rotational reactive effects. It is the combination of these motions that produces the effective polishing action of this device. The driving motion is slightly modified by the angular placement of the working surface of the polishing tool and by its inherent elasticity. The net effect is the production of a vibratory polishing force directed along the tooth face but with a component vertical to the surface. This produces a desirable rolling action to the abrasive particles and causes them to present continually new working surfaces for the polishing action upon the toot-h surface.

From the foregoing description, it will be seen that a simple, efficient, and economical means has been provided for accomplishing all of the objects and advantages of the invention.

I claim:

1. In a dental tool driving mechanism the combination of:

a body member of generally cylindrical shape having a cylindrical axial bore, an air driven free piston reciprocable vibratory motor Within said body adapted to impart vibratory motion to said body as a whole along the longitudinal axis thereof,

the cylindrical bore of said body characterized by a section of unit diameter including a section of limited but limited length adjacent to and on the opposite side of said air inlet, and by a further section of enlarged diameter, including an air exhaust passage through the cylinder wall, located beyond the seclength of larger diameter located between a sealing 5 tion of reduced diameter,

end cap and an air inlet through the cylinder wall, a piston characterized by a head section of a diameter by a section of reduced diameter but limited length for sliding fit within the cylinder bore of unit diadjacent to and on the opposite side of said air inlet, ameter, and by a second section of reduced diameter and by a further section of enlarged diameter, includfor sliding tit within the bore section of reduced ing an air exhaust passage through the cylinder wall, 10 diameter,

located beyond the section of reduced diameter, the piston diameters proportioned to give equal thrust the piston of the said motor characterized by a head in each direction,

section of a diameter for sliding fit within the cylinder a bore within the piston extending from the head end bore of unit diameter and by a second section of to intersection with exhaust ports through the piston reduced diameter, forming a st p n i p n, for Wall in the section of reduced diameter and adjacent sliding fit within the bore section of reduced diameter, the outer end thereof,

the piston diameters proportioned to give equal thrust inlet ports through the piston wall in the section of in each direction, large diameter intersecting said piston bore,

a bore Within Piston extending from the head end said piston inlet ports cooperating With the piston step to intersection with radial exhaust ports through the d th cylinder section of increased diameter to piston wall in the section of red ced di ete a d determine the inlet and cutolf events of the air motor, adjacent the Outer 611d thelfiof, and the piston exhaust ports cooperating with the radial inlet ports through the piston wall in the section li d se ti n of reduced diameter to determine of large diameter also intersecting said piston bore, th li and exhaust events of the motor,

the said inlet ports cooper ing With the Piston p whereby said free piston is driven in a substantially and the cylinder section of increased diameter to i o ating motion longitudinally of said bore determine the inlet and cutoff events of the air th b imparting a e tive motion to the head for motor and the Piston exhaust POrts cooperating the purpose of driving the tool mounted thereon in with the cylinder section of reduced diameter to a f l k th determine the sealing and exhaust events of the motor, References Cited by the Examiner together with fixed tool mounting means at the outer UNITED STATES PATENTS extremity of said body adapted to hold a tool immovable with respect to said body, the said mount- 443691 12/1890 West, 32-56 ing means being driven in a useful work path solely 35 477,411 6/1892 Hams 3256 as a result of the reactive vibratory motion of said 1O46560 12/1912 coulson 3247 cylindrical body member due to the vibration of the 1324,0239 4/1917 Hawley free piston therewithim 1,641,031 8/1927 Galllard 3254 2, An improvement in air driven reciprocating driving 2,937,444 5/1960 Kern 3227 mechanisms for dental tools of the class wherein the tool OTHER REFERENCES is fixedly mounted upon a generally cylindrical tool holding head, comprising the combination of:

.a concentric longitudinal cylindrical bore of unit diameter within the head characterized by a section of increased diameter but limited length located between a sealing end cap and an air inlet through the cylinder wall, by a section of reduced diameter Dentist's Supply Co. (British) 847,262, Sept. 7, 1960, 22 pages spec. 4 shts. dwg.; see page 7.

RICHARD A. GAUDET, Primary Examiner.

JOHN R. KLINE, HAROLD B. WHITMORE, ROBERT E. MORGAN, Examiners. 

1. IN A DENTAL TOOL DRIVING MECHANISM THE COMBINATION OF: A BODY MEMBER OF GENERALLY CYLINDRICAL SHAPE HAVING A CYLINDRICAL AXIAL BORE, AN AIR DRIVEN FREE POSITION RECIPROCABLE VIBRATORY MOTOR WITHIN SAID BODY ADAPTED TO IMPART VIBRATORY MOTION TO SAID BODY AS A WHOLE ALONG THE LONGITUDINAL AXIS THEREOF, THE CYLINDRICAL BORE OF SAID BODY CHARACTERIZED BY A SECTION OF UNIT DIAMETER INCLUDING A SECTION OF LIMITED LENGTH OF LARGER DIAMETER LOCATED BETWEEN A SEALING END CAP AND AN AIR INLET THROUGH THE CYLINDER WALL, BY A SECTION OF REDUCED DIAMETER BUT LIMITED LENGTH ADJACENT TO AND ON THE OPPOSITE SIDE OF SAID AIR INLET, AND BY A FURTHER SECTION OF ENLARGED DIAMETER, INCLUDING AN AIR EXHAUST PASSAGE THROUGH THE CYLINDER WALL, LOCATED BEYOND THE SECTION OF REDUCED DIAMETER, THE PISTON OF THE SAID MOTOR CHARACTERIZED BY A HEAD SECTION OF A DIAMETER FOR SLIDING FIT WITHIN THE CYLINDER BORE OF UNIT DIAMETER AND BY A SECOND SECTION OF REDUCED DIAMETER, FORMING A STEP ON SAID PISTON, FOR SLIDING FIT WITHIN THE BORE SECTION OF REDUCED DIAMETER, THE PISTON DIAMETERS PROPORTIONED TO GIVE EQUAL THRUST IN EACH DIRECTION, A BORE WITHIN THE PISTON EXTENDING FROM THE HEAD END TO INTERSECTION WITH RADIAL EXHAUST PORTS THROUGH THE PISTON WALL IN THE SECTION OF REDUCED DIAMETER AND ADJACENT THE OUTER END THEREOF, RADIAL INLET PORTS THROUGH THE PISTON WALL IN THE SECTION OF LARGE DIAMETER ALSO INTERSECTING SAID PISTON BORE, THE SAID INLET PORTS COOPERATING WITH THE PISTON STEP SAID THE CYLINDER SECTION OF INCREASED DIAMETER TO DETERMINE THE INLET AND CUTOFF EVENTS OF THE AIR MOTOR AND THE PISTON EXHAUST PORTS COOPERATING WITH THE CYLINDER SECTION OF REDUCED DIAMETER TO DETERMINED THE SEALING AND EXHAUST EVENTS OF THE MOTOR, TOGETHER WITH FIXED TOOL MOUNTING MEANS AT THE OUTER EXTREMITY OF SAID BODY ADAPTED TO HOLD A TOOL IMMOVABLE WITH RESPECT TO SAID BODY, THE SAID MOUNTING MEANS BEING DRIVEN IN A USEFUL WORK PATH SOLELY AS A RESULT OF THE REACTIVE VIBRATORY MOTION OF SAID CYLINDRICAL BODY MEMBER OF THE VIBRATION OF THE FREE PISTON THEREWITHIN. 